1. Field of the Invention
The present invention relates to a susceptor with a built-in plasma generation electrode and a manufacturing method therefor. In particular, it relates to a susceptor with a built-in plasma generation electrode that has excellent corrosion resistance and plasma resistance, that can enable uniform etching of plate specimens, deposition of film and so forth, and that has excellent durability, and a manufacturing method for a susceptor with a built-in plasma generation electrode that enables a susceptor with a built-in plasma generation electrode to be manufactured economically and with a high yield.
2. Description of the Related Art
In recent years, in plasma etching apparatus, plasma CVD apparatus and the like used in manufacturing processes of semiconductor devices such as ICs, LSIs and VLSIs, in order to perform film deposition uniformly on each wafer by plasma etching or plasma CVD, these wafers (plate specimens) are mounted onto a specimen support (pedestal) called a susceptor, and prescribed processing is carried out.
Because this susceptor must withstand use within plasma and use at high temperatures, the susceptor must have excellent plasma resistance and high heat conductivity.
For such a susceptor, a susceptor formed from a ceramic sintered body having excellent plasma-resistance and thermal conductivity is used.
Heretofore, as an example of a susceptor formed from such a ceramic sintered body, a susceptor with a built-in plasma generation electrode as shown in FIG. 7 is known.
This susceptor with a built-in plasma generation electrode 1 comprises: a mounting plate 2, the upper surface of which serves as a mounting surface 2a on which a plate specimen such as a wafer or the like is mounted; a support plate 3 which is unified with this mounting plate 2 to support the mounting plate 2; a plasma generation electrode 4 which is formed between the mounting plate 2 and the support plate 3; and a power supply terminal 6 which is installed in a fixing hole 5 passing through the support plate 3 and makes contact with the plasma generation electrode 4, and which also supplies external high frequency current to the plasma generation electrode 4.
The above-described mounting plate 2 is flat and formed from an insulated ceramic sintered body, the support plate 3 is flat and formed from a insulated ceramic sintered body, and a susceptor substrate 7 is created by the mounting plate 2 and the support plate 3.
Furthermore, the plasma generation electrode 4 comprises conductive layers whose main constituents are metals with high melting points such as tungsten (W), molybdenum (Mo), tantalum (Ta), niobium (Nb), and the like, and the value of whose resistance is uniform over these conductive layers.
The power supply terminal 6 is a rod whose main constituents are high melting point metals such as tungsten (W), molybdenum (Mo), tantalum (Ta), niobium (Nb) and the like.
In order to manufacture this susceptor with a built-in plasma generation electrode 1, firstly the fixing hole 5 passing perpendicularly through the support plate 3 is formed at a predetermined location, and the power supply terminal 6 is fixed into this fixing hole 5.
Next, this support plate 3 is coated with a conductive coating material 7 containing a high melting point metal powder so as to make contact with the power supply terminal 6, and then dried. After this, the support plate 3 and the mounting plate 2 are superposed via the coated surface of this conductive coating material 7 and are unified by heat treatment under pressure, and also a plasma generation electrode 4 is formed between the support plate 3 and the mounting plate 2 by applying heat treatment to the conductive coating material 7.
As above, a susceptor with a built-in plasma generation electrode 1 can be obtained in which the plasma generation electrode 4 and the power supply terminal 6 are joined reliably and firmly.
However, the susceptor 1 as described above has a problem in that, because the surface uniformity of a plate specimen of a wafer or the like is not always even after a process that uses plasma, such as deposition, etching and the like of the plate specimen, non-uniformity in the characteristics of the obtained semiconductor device is significant.
Especially as wafer diameters have increased in recent years, since non-uniformities of wafer surface characteristics must be minimized as much as possible, a susceptor, including a susceptor with a built-in plasma generation electrode that further enhances the uniformity of the surface after processing in a range of plasma processes has been much sought after.
Furthermore, cracking occurs easily in the vicinity of the connection of the plasma generation electrode 4 and the power supply terminal 6, so that there is a problem in that durability of a susceptor with a built-in plasma generation electrode is not sufficient.
The present invention aims to solve the above-described problems with an object of providing a susceptor with a built-in plasma generation electrode that can make the throughput in a range of plasma processes on a mounted plate specimen more uniform, and which also has excellent plasma-resistance, thermal conductivity and durability, and a manufacturing method that allows a susceptor with a built-in plasma generation electrode to be produced easily and economically.
As a result of intensive research, the inventors discovered that in a conventional susceptor with a built-in plasma generation electrode, since the region in the vicinity of the connection of the plasma generation electrode and the power supply terminal becomes a high current density region during plasma generation, abnormal heat generation occurs easily in the vicinity of this connection, and consequently the throughput in a range of plasma processes on a mounted plate specimen becomes non-uniform. Moreover, they discovered that since cracking occurs easily in the vicinity of this connection, the durability of a susceptor with a built-in plasma generation electrode is not sufficient. Therefore, the inventors realized that if a part being a high current density region in a plasma generation electrode, that is the region in the vicinity of the connection of the plasma generation electrode and the power supply terminal, is made to be low resistance, then the above problem can be solved effectively, thereby arriving at the present invention.
In other words, a susceptor with a built-in plasma generation electrode of the present invention comprises: a susceptor substrate formed from a ceramic, one principal plane of which is a mounting surface on which a plate specimen is mounted; a plasma generation electrode built into this susceptor substrate; and a power supply terminal which is located so as to pass through the susceptor substrate and connected to the plasma generation electrode, wherein a region in the vicinity of the connection of the plasma generation electrode to the power supply terminal has a lower resistance than other regions of the plasma generation electrode.
In this susceptor with a built-in plasma generation electrode, since the region in the vicinity of the connection of the plasma generation electrode to the power supply terminal has a lower resistance than the other regions, abnormal heat generation is suppressed in the region (low resistance region) in the vicinity of the connection of the plasma generation electrode to the power supply terminal, so that the heat of the susceptor substrate is made uniform. This improves the heat uniformity of the mounting surface of the susceptor substrate, resulting in an improvement in heat uniformity of a plate specimen mounted onto the mounting surface, and the throughput by plasma processing of the plate specimen is made uniform. Furthermore, as a result of the improvement in heat uniformity of the mounting surface of the susceptor substrate, durability is improved significantly.
Preferably, the susceptor substrate comprises a mounting plate formed from a ceramic, one principal plane of which is a mounting surface on which a plate specimen is mounted, and a support plate formed from a ceramic, which is joined and unified with the mounting plate.
With such a construction, it is possible to position the plasma generation electrode at a desired location on the susceptor substrate. Furthermore, since it is possible to connect the plasma generation electrode and the power supply terminal reliably and firmly, reliability of electrical contact is improved.
Preferably, an insulating layer that has at least the same principal ingredient as the support plate and the mounting plate, is formed in the regions on the support plate excluding the plasma generation electrode. With such a construction, insulation of the plasma generation electrode is enhanced.
Preferably, the ceramic is an aluminum oxide based ceramic or an aluminum nitride based ceramic.
The low resistance region of the plasma generation electrode is preferably of a multilayer structure containing a total of two or more conductive ceramic layers and/or composite conductive ceramic layers.
Preferably, the multilayer structure is a three layer structure in which the composite conductive ceramic layer, the conductive ceramic layer or high melting point metal layer, and the composite conductive ceramic layer are stacked in sequence.
It is preferable that the composite conductive ceramic layer is of a type selected from an aluminum oxide and tantalum carbide composite conductive ceramic, an aluminum oxide and molybdenum carbide composite conductive ceramic, and an aluminum oxide and tungsten composite conductive ceramic, that the conductive ceramic layer is a tantalum carbide conductive ceramic or molybdenum carbide conductive ceramic, and that the high melting point metal layer is tantalum or tungsten.
Furthermore, the composite conductive ceramic layer may be an aluminum nitride and tungsten composite conductive ceramic or an aluminum nitride and molybdenum composite conductive ceramic, and the high melting metal layer may be tungsten or molybdenum.
A manufacturing method for a susceptor with a built-in plasma generation electrode of the present invention comprises the steps of: manufacturing a mounting plate on which a plate specimen is mounted and a support plate that supports the mounting plate using ceramics; then forming an open hole in the support plate and inserting and fixing a power supply terminal into this open hole; then coating with a first electrode coating material containing conductive powder on one principal plane of the support plate so as to make contact with the power supply terminal to form a first plasma generation electrode forming layer; then coating with a second electrode coating material containing conductive powder with a higher resistance than the first electrode coating material in the regions on the principal plane of the support plate excluding the first plasma generation electrode forming layer, to form a second plasma generation electrode forming layer with a higher resistance than the first plasma generation electrode forming layer; then superposing the mounting plate onto the support plate via the first and second plasma generation electrode forming layers, heat treating under pressure to form a plasma generation electrode having a low resistance region and a high resistance region between the support plate and the mounting plate, and joining and unifying them.
In this manufacturing method for a susceptor with a built-in plasma generation electrode, by forming a first plasma generation electrode forming layer, being a low resistance region, and a second plasma generation electrode forming layer, being a higher resistance region than the first plasma generation electrode forming layer, on the interface between the mounting plate and the support plate, formed from ceramics, and by heat treating the support plate and the mounting plate together with the first and second plasma generation electrode forming layers under pressure, abnormal heat generation in the region in the vicinity of the connection of the plasma generation electrode to the power supply terminal is suppressed, so that heat uniformity of the mounting surface of the susceptor substrate is improved, and the throughput by plasma processing of a plate specimen that is mounted onto this mounting surface is made uniform. Moreover, it is possible to manufacture a susceptor with a built-in plasma generation electrode, whose durability is improved significantly, economically and with a high yield.
Another manufacturing method for a susceptor with a built-in plasma generation electrode of the present invention comprises the steps of: manufacturing a mounting plate green body on which a plate specimen is mounted and a support plate green body that supports the mounting plate using a slurry containing ceramic powder; then forming an open hole in the support plate green body, and packing power supply forming material containing conductive powder, or inserting a power supply terminal, into this open hole; then coating with a first electrode coating material containing conductive powder on one principal plane of the support plate green body so as to make contact with the power supply forming material or the power supply terminal to form a first plasma generation electrode forming layer; then coating with a second electrode coating material containing conductive powder with a higher resistance than the first electrode coating material in the regions on the principal plane of the support plate green body excluding the first plasma generation electrode forming layer, to form a second plasma generation electrode forming layer with a higher resistance than the first plasma generation electrode forming layer; then superposing the mounting plate green body onto the support plate green body via the first and second plasma generation electrode forming layers, and heat treating under pressure to form a plasma generation electrode having a low resistance region and a high resistance region between the support plate and the mounting plate, formed from ceramics, and joining and unifying them.
In this manufacturing method for a susceptor with a built-in plasma generation electrode, by forming a first plasma generation electrode forming layer, being a low resistance region, and a second plasma generation electrode forming layer, being a higher resistance region than the first plasma generation electrode forming layer, on the interface between the mounting plate green body and the support plate green body, and by heat treating the support plate green body and the mounting plate green body together with the first and second plasma generation electrode forming layers under pressure, abnormal heat generation in the region in the vicinity of the connection of the plasma generation electrode to the power supply terminal is suppressed, so that heat uniformity of the mounting surface of the susceptor substrate is improved, and the throughput by plasma processing of a plate specimen that is mounted onto this mounting surface is made uniform. Moreover, it is possible to manufacture a susceptor with a built-in plasma generation electrode whose durability is improved significantly, by one heat treatment, economically and with a high yield.
In both of the manufacturing methods described above, a method is desirable wherein by forming an insulation material layer containing ceramic powder, which has at least the same principal ingredient as the support plate or the support plate green body, in the regions on one principal plane of the support plate or the support plate green body excluding the first and second plasma generation electrode forming layers, and then heat treating under pressure, the insulation material layer is made to be an insulating layer.
By employing such a method, it is possible to manufacture a susceptor with a built-in plasma generation electrode with the insulation of the plasma generation electrode further enhanced.
Furthermore, the ceramic is preferably an aluminum oxide based ceramic or an aluminum nitride based ceramic.
Moreover, it is preferable that the first plasma generation electrode forming layer is made a three layer structure by forming a first layer using a composite conductive ceramic layer forming coating agent, forming a second layer using a conductive ceramic layer forming coating agent or a high melting point metal layer forming coating agent, and forming a third layer using a composite conductive ceramic layer forming coating agent.
Furthermore, it is preferable that the composite conductive ceramic layer forming coating agent contains one powder selected from; an aluminum oxide and tantalum carbide composite conductive ceramic powder, an aluminum oxide and molybdenum carbide composite conductive ceramic powder, and an aluminum oxide and tungsten composite conductive ceramic powder, the conductive ceramic layer forming coating agent contains a tantalum carbide conductive ceramic powder or a molybdenum carbide conductive ceramic powder, and the high melting point metal layer forming coating agent contains tantalum powder or tungsten powder.
Moreover, the composite conductive ceramic layer forming coating agent may contain an aluminum nitride and tungsten composite conductive ceramic powder, or an aluminum nitride and molybdenum composite conductive ceramic powder, and the high melting point metal layer forming coating agent may contain tungsten powder or molybdenum powder.